CBSE Class 12 Physics Viva Questions and Answers 2025- The Physics Viva for CBSE Class 12 practical exams is aimed at checking a student’s knowledge of the related content, practical abilities, and problem-solving skills. Students should also be able to do the following: …explain their experimental set-up, and observation, as well as the observations made based on the scientific principles of the experiments performed. Here are some typical general questions with their answers that will in one way or the other assist you in preparation.
1. How does a barometer work?
Answer: A barometer makes use of pressure disparity as the main determinant. This consists of a long tube containing mercury that is inverted in a container having mercury also. The atmospheric pressure is read from the disparity of the distance that has ascended up the height of the mercury column in the tube. When the pressure of the air goes up the column of mercury goes up, and if the pressure comes down the column of mercury comes down.
2. Can you explain what scalar and vector quantities are?
Answer:
- Scalar quantities: These are quantities that have only a value and have no orientation in space (for example, mass, temperature and speed).
- Vector quantities: These have both size and sense (for example, force, velocity, displacement).
3. What is Ohm’s Law?
Answer: Ohm’s Law simply states is the linear relationship between the current and voltage on the conductor circuit is inversely related to the resistance of the conductor.
V=IRV = IRV=IR Where:
VVV is the potential difference,
III is the current,
It is the resistance.
4. What are the parameters determining the degree of resistance within a conductor?
Answer:
The resistance of a conductor depends on the following factors:
- Length of the conductor: Resistance is directly proportional to the length of the conductor.
- Area of cross-section: Hence resistance is inversely proportional to the cross-sectional area.
- Material of the conductor: There are eminent variations in the resistivities of different materials which cause changes in the resistance.
- Temperature: For most of the materials there is a general trend of resistance increasing with temperature.
5. What is the law of reflection?
Answer: The law of reflection states that the angle of incidence is equal to the angle of reflection. Both angles are measured concerning the normal (an imaginary line perpendicular to the reflecting surface).
6. What is the refractive index of a medium?
Answer: The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in the medium.
n=cvn = \frac{c}{v}n=vc
Where:
- N is the refractive index,
- ccc is the speed of light in a vacuum,
- V is the speed of light in the medium.
7. What is the principle of superposition of waves?
Answer: The principle of superposition states that when two or more waves meet at a point, the resultant displacement at that point is the algebraic sum of the displacements of the individual waves at that point. This principle applies to both mechanical and electromagnetic waves.
8. What is the difference between interference and diffraction?
Answer:
- Interference: Interference is the phenomenon that occurs when two or more waves overlap and combine to form a resultant wave. The resulting wave can be constructive (when waves reinforce each other) or destructive (when waves cancel each other out).
- Diffraction: Diffraction refers to the bending of waves around obstacles or the spreading of waves when they pass through small openings.
9. What is the working principle of a moving coil galvanometer?
Answer: A moving coil galvanometer works on the principle that when a current flows through a coil placed in a magnetic field, a torque is exerted on the coil, causing it to rotate. The amount of rotation is proportional to the current passing through the coil. The galvanometer is calibrated to measure the current.
10. What is the difference between AC and DC?
Answer:
- Alternating Current (AC): The current that reverses direction periodically. The magnitude of the current also varies sinusoidally with time (e.g., the electricity supplied to homes).
- Direct Current (DC): The current flows in a single direction with a constant magnitude (e.g., battery-powered devices).
11. What is the principle behind the working of an electric motor?
Answer: An electric motor works on the principle of the force experienced by a current-carrying conductor in a magnetic field. When a current passes through a coil in a magnetic field, a force is exerted on the coil, causing it to rotate. This rotational motion is then used to perform mechanical work.
12. What is the relation between current, voltage, and power?
Answer: The relationship between current, voltage, and power is given by the equation:
P=IVP = IVP=IV
Where:
- PPP is the power (in watts),
- III is the current (in amperes),
- VVV is the voltage (in volts).
Power can also be expressed as:
P=I2RP = I^2RP=I2R or P=V2RP = \frac{V^2}{R}P=RV2, where RRR is the resistance.
13. What is the principle of a transformer?
Answer: A transformer works on the principle of electromagnetic induction. It uses two coils of wire (primary and secondary) wound around a magnetic core. When alternating current flows through the primary coil, it produces a varying magnetic field, which induces a voltage in the secondary coil. The voltage change is proportional to the ratio of the number of turns in the primary and secondary coils.
Conclusion
These viva questions are designed to help students get a strong grasp of core concepts and principles in Physics. By understanding and practising these answers, students can be confident in handling their practical exams.
Good luck with your preparations for the CBSE Class 12 Physics practicals!
